JP2006046211A - Method and device for supplying lpg fuel to engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make low temperature startability of an engine better by not injecting LPG fuel which is liquid in a vaporizer during operation with accompanying temperature rise in a method for supplying LPG fuel to the engine using heat of an electric heater for heating LPG fuel at low temperature start. <P>SOLUTION: In the method for supplying LPG fuel to the engine vaporizing fuel by a vaporizer 3 using engine cooling water after warming up and an electric heating part 3b using an electric heater at an early stage of low temperature start as heat source and sending the same to a fuel injection valve 5 and injecting the same to an intake pipe 4b of the engine, a second shut off valve 2b controlled by an electronic control unit 10 is arranged in a fuel inlet side of the vaporizer 3, quantity of LPG fuel flowing in the vaporizer 3 using the electric heating part 3b as the heat source is limited at the early stage of low temperature start to prevent liquid LPG fuel in a pre-heater chamber 30 from being pressed out by generated vaporized gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for supplying vaporized gas obtained by vaporizing LPG (liquefied petroleum gas) fuel to an engine, and an apparatus therefor, in particular, utilizing heat of engine cooling water after warm-up as means for heating and vaporizing LPG fuel. In addition to the above, the present invention relates to an LPG fuel supply method and apparatus for improving engine startability by utilizing heat generated from an electric heater at low temperature start.

  LPG has been used as a fuel for spark ignition engines from the past. The LPG fuel stored in the fuel tank is vaporized gas reduced to atmospheric pressure using a vaporizer (regulator) and a mixer, and the intake pipe of the engine Is widely used, and for example, as described in Japanese Patent Application Laid-Open No. 6-17709, a method of adjusting the vaporized gas to a predetermined positive pressure and injecting it into the intake pipe of the engine Is also widely known.

  And in the system which adjusts this LPG fuel to the vaporization gas of predetermined positive pressure, using the heat of the engine cooling water warmed up as a means to heat-vaporize LPG fuel is used conventionally. However, the heating and vaporizing means using the heat of the engine cooling water does not sufficiently vaporize the LPG fuel because the cooling water is at a low temperature when the engine is cold. This makes it difficult to start the engine.

  Therefore, as described in, for example, JP-A-5-223014 and JP-A-11-324813, in a vaporizer for depressurizing and vaporizing LPG fuel, an electric heater is disposed in the path of the LPG fuel and cooled. Means have been proposed in which LPG fuel can be vaporized even when the temperature of water is low.

However, since the electric heater requires a predetermined time until it rises to a temperature suitable for vaporization of LPG fuel, the vaporizer preheater chamber is filled with LPG fuel until then, and the internal temperature increases as the temperature of the electric heater increases. When the LPG fuel stored in the gas is rapidly vaporized, the LPG fuel is pushed out from the vaporizer by the pressure and ejected from the fuel injection valve, which may cause engine malfunction or engine stop at low temperature start.
JP-A-6-17709 Japanese Patent Laid-Open No. 5-223014 Japanese Patent Laid-Open No. 11-324813

  The present invention is intended to solve the above-described problems. In addition to using engine cooling water after warm-up as a heat source for heat vaporization of LPG fuel, an electric heater is used at low temperature start. The LPG fuel supply method and apparatus for improving the startability of the engine with the low temperature of the engine by preventing the LPG fuel in the vaporizer from being ejected from the fuel injection valve as the temperature of the electric heater rises during low temperature start of the engine. The biggest challenge is to improve the startability.

  Therefore, the present invention vaporizes the liquid LPG fuel stored in the fuel tank with a vaporizer that uses the engine cooling water as a heat source after warm-up and uses an electric heating unit using an electric heater as a heat source at the beginning of low temperature start. In an LPG fuel supply method for an engine that is fed to a fuel injection valve and injected into an intake pipe of the engine, a shut-off valve controlled by an electronic control unit is arranged on the fuel inlet side of the vaporizer, The amount of LPG fuel that flows into the vaporizer with the heat source as the heat source is limited.

  With this configuration, the LPG fuel flowing into the vaporizer from the electronic control unit at the initial start of the engine from when the key is turned on until the start of the starter motor operation is converted into vaporizer by the vaporized gas generated as the temperature of the electric heater rises. Since it is possible to limit the amount not to be pushed out, it is possible to easily avoid the engine trouble caused by the LPG fuel injection at the low temperature start.

  Further, if the electronic control unit controls the opening time of the shut-off valve based on predetermined data monitored by the electronic control unit using at least one type of sensor, it can vaporize the LPG fuel. The opening / closing control of the shut-off valve can be made accurate by finely responding to fluctuations in each parameter that affects the shut-off valve.

  Further, if the sensor includes a fuel pressure sensor disposed in the vaporizer or downstream thereof, and if the detected fuel pressure exceeds a predetermined pressure, the shut-off valve is closed, the rapid rise in the vaporizer. The amount of inflow of LPG fuel can be limited before the start of proper LPG fuel vaporization, and the LPG fuel can be prevented from being pushed out of the vaporizer.

  Furthermore, the valve opening time of the shut-off valve is calculated by a predetermined calculation formula using the predetermined data described above by the electronic control unit, and the LPG fuel is vaporized by the vaporized gas generated as the temperature of the electric heater rises. If the amount of LPG fuel inflow that is the maximum storage amount that is not pushed out is limited, it becomes easy to secure a necessary and sufficient amount of fuel supply while reliably avoiding LPG fuel injection.

  Furthermore, a vaporizer provided with warm water heating means using engine cooling water and electric heating means using an electric heater, a shut-off valve disposed on the vaporizer inlet side of the fuel supply line, and an electronic device that controls opening and closing of the shut-off valve If the LPG fuel supply device for an engine that includes the control unit and implements the above-described LPG fuel supply method is used, the above-described operations and effects can be easily realized.

  According to the present invention in which the amount of LPG fuel flowing into the vaporizer is limited to a predetermined amount at the initial start of the engine at a low temperature, the LPG fuel is easily pushed out of the vaporizer and ejected from the fuel injection valve as the temperature of the electric heater rises. This can be avoided, and the low temperature startability of the engine can be improved.

  An embodiment of the present invention will be described with reference to the drawings. In FIG. 1 showing a layout of an engine provided with an LPG fuel supply device for carrying out the LPG fuel supply method of the present embodiment, LPG fuel is stored, and a fuel supply line 9 </ b> A extending from the fuel tank 1 is connected to the vaporizer 3. In the fuel supply line 9A, a first shut-off valve 2a is disposed near the fuel tank 1 outlet, and a second shut-off valve 2b is disposed near the vaporizer 3 inlet.

  The vaporizer 3 depressurizes and vaporizes LPG fuel from a liquid fuel state to adjust to a vaporized gas having a predetermined pressure, and is provided with a hot water heating unit 3a using engine cooling water as a heat source on the inlet side, and downstream thereof. An electric heating unit 3b using an electric heater as a heat source is provided on the side, and a pressure regulating unit 3c is further provided on the downstream side. A fuel supply line 9 </ b> B extending from the vaporizer 3 is connected to a fuel injection valve 5 installed in the intake line 4 b of the engine 4.

  The vaporizer 3 and the hot water heating unit 3b provided in the vaporizer 3 have the same configuration as a commonly used vaporizer (regulator), and a cooling water jacket 4a provided in the engine 4 and a hot water heating unit 3a are provided. The engine coolant is circulated through the cooling water passages 8a and 8b, and the vaporized gas generated by heating the LPG fuel with the heat is adjusted to a positive pressure of a predetermined pressure by the pressure adjusting unit 3c, and the fuel supply line It is sent to 9B.

  In addition, the electric heating unit 3b provided on the downstream side of the hot water heating unit 3a has a flat PTC heater, which is an electric heater (not shown), stacked with a heat transfer plate in close contact with the front and rear surfaces and surrounds the periphery with a peripheral wall. In the preheater chamber 30, which is a space for introducing and storing LPG fuel, the heater unit 31 that is in a gas / liquid tight state is accommodated so as to have a space on the entire outer periphery thereof, and performs heat exchange. The heat transfer plate of the heater unit 31 also serves as an electrode and is connected to a battery (not shown) and is connected to the electronic control unit 10 to control the energization thereof.

  The electronic control unit 10 uses a general engine control program installed in the storage means. In addition to the normal fuel injection control function, the engine from the time when the key is turned on until the start of the starter motor is started. In the initial stage of startup, the second shut-off valve 2b disposed on the vaporizer 3 inlet side of the fuel supply line 9A is controlled to open and close to limit the amount of LPG fuel flowing into the vaporizer 3 within a predetermined amount. It is characterized by having.

  That is, the electronic control unit 10 sequentially monitors the fuel pressure data detected by the fuel pressure sensor 11 disposed in the preheater chamber 30 in order to control the opening / closing of the second shutoff valve 2b at the time of cold start. In addition to this, fuel pressure data from the fuel pressure sensor 12 disposed in the fuel supply line 9B, and coolant temperature data from the coolant temperature sensor 13 disposed in the coolant passage 8a. The engine speed data from the engine speed monitor 14 provided in the engine 4 is also monitored sequentially.

  Then, the electronic control unit 10 detects the engine coolant temperature by the coolant temperature sensor 13 when the key is turned on, and determines whether it is necessary to heat the LPG fuel using the electric heating unit 3b. When it is determined that the LPG fuel needs to be electrically heated, the heater unit 31 is instructed to be energized, but at the same time, the fuel pressure is detected using the fuel pressure sensor 11 provided in the preheater chamber 30. It is like that. On the other hand, when it is determined that it is not necessary to electrically heat the LPG fuel, the energization to the heater unit 31 is not instructed, and the valve opening time of the second shutoff valve 2b at the initial start of the engine 4 is not required. Therefore, the second shutoff valve 2b is kept open.

  When the engine coolant temperature is low, the electronic control unit 10 commands the energization of the heater unit 31 and sequentially monitors the fuel pressure in the pre-heater chamber 30. When the fuel pressure exceeds a predetermined pressure, the second cutoff is performed. The valve 2b is closed to limit the amount of LPG fuel flowing into the vaporizer 3. Further, this closed state is terminated at the beginning of the engine 4, that is, at the same time as the end of the remaining heat period, and the second shutoff valve 2b is opened.

  In addition, in addition to the fuel pressure data of the preheater chamber 30, the opening time of the second shut-off valve 2b at the beginning of the engine start at a low temperature is added to the fuel pressure data of the fuel supply line 9B, the engine coolant temperature data, and the engine speed. Based on the data, the vaporization state of the LPG fuel is grasped by using a predetermined calculation method, and the subsequent vaporization amount is estimated. Based on this, the preheater chamber 30 is determined by the pressure of the vaporized gas accompanying the temperature rise of the heater unit 31. It is possible to control the valve opening operation of the second shut-off valve 2b more accurately by calculating the maximum storage amount in which the LPG fuel is not pushed out of the vaporizer 3 and determining it to coincide with this amount. Become.

  Hereinafter, with respect to the operation of the LPG fuel supply apparatus according to the present embodiment, the operation of the conventional LPG fuel supply apparatus shown in FIG. This will be explained in comparison with Example).

  When the engine 4 is started, when the ignition key is turned and the ignition signal is turned ON, the cooling water temperature is detected by the cooling water temperature sensor 13 via the electronic control unit 10 to determine whether or not the electric fuel needs to be heated. The electric heater energization signal is turned ON when it is determined that electrical heating is necessary. Simultaneously, an ON signal is sent to the electromagnetically driven first shut-off valve 2a and the second shut-off valve 2b so that both are opened.

  The electronic control unit 10 starts monitoring the fuel pressure in the preheater chamber 30 via the fuel pressure sensor 11 by turning on the electric heater energization signal, and the fuel pressure value is equal to or higher than a predetermined pressure value. Then, the second shutoff valve 2b is closed to restrict the inflow of LPG fuel into the vaporizer 3. That is, in the comparative example shown in FIG. 2 (B), the valve open signal of the second shutoff valve 2b on the vaporizer 3 inlet side is turned on and the valve open state is maintained as it is, whereas FIG. In this embodiment, the electronic control unit is configured to close the second shut-off valve 2b for a predetermined time after the second shut-off valve 2b is opened until the end of the remaining heat period (when the starter motor starts). 10 controls to limit the amount of fuel flowing into the vaporizer 3 to about 1/3.

  As described above, since the flow rate of the LPG fuel flowing into the vaporizer 3 after the opening of the second shutoff valve 2b is limited to an appropriate amount by a command from the electronic control unit 10 at the initial stage of engine startup, the temperature of the heater unit 31 is sufficiently increased. A predetermined proportion of space (gas phase) can be secured in the preheater chamber 30 until the LPG fuel (liquid phase) stored in the preheater chamber 30 is pushed out of the vaporizer 3 and discharged from the fuel injection valve 5. The situation of erupting can be surely avoided.

  As described above, the electronic control unit 10 uses the fuel pressure data in the fuel supply line 9B, the engine coolant data, the engine speed data, etc. in addition to the fuel pressure data from the fuel pressure sensor 11, and the heater unit 31. When calculating the maximum storage amount in which the LPG fuel is not pushed out of the vaporizer 3 by the vaporized gas generated in the preheater chamber 30 as the temperature rises, the second amount is set so as to coincide with the inflow amount of fuel that becomes the maximum storage amount. The valve opening time of the shutoff valve 2b is controlled. Thus, it is possible to easily ensure the supply of the minimum fuel necessary for starting the engine while avoiding the LPG fuel being pushed out of the vaporizer 3 at the time of starting the engine at a low temperature.

  Further, in addition to or instead of the fuel pressure data of the preheater chamber 30 as data for the electronic control unit 10 to determine the closing of the second shutoff valve 2b in the initial low temperature start of the engine, the fuel supply line 9B If the fuel pressure data, the coolant temperature data, the engine speed data, etc. are used in appropriate combination, more accurate control can be realized.

  As described above, the inflow amount is limited by the LPG fuel supply device of the present embodiment that implements the fuel supply method of the present invention so that the LPG fuel is not excessively stored in the vaporizer 3 at the initial low temperature start of the engine 4. As a result, it is possible to easily avoid the LPG fuel being pushed out by the vaporized gas generated as the temperature of the electric heater rises and ejected from the fuel injection valve 5, so that the low temperature startability of the engine is improved. Is something that can be done.

The layout which shows embodiment of this invention. (A) is a waveform diagram of each signal at the time of cold start in the embodiment of FIG. 1, (B) is a waveform diagram of each signal at the time of cold start in the comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel tank, 2a 1st cutoff valve, 2b 2nd cutoff valve, 3 Vaporizer, 3a Hot water heating part, 3b Electric heating part, 3c Pressure regulation part, 4 Engine, 4b Intake pipe line, 5 Fuel injection valve, 9A, 9B Fuel supply line, 10 electronic control unit, 11, 12 fuel pressure sensor, 13 cooling water temperature sensor, 14 engine speed monitor, 30 preheater chamber, 31 heater unit

Claims (5)

  The liquid LPG fuel stored in the fuel tank is vaporized by a vaporizer that uses the engine heating water as a heat source after warm-up and an electric heating part using an electric heater as a heat source at the beginning of low temperature start, and becomes a fuel injection valve In an LPG fuel supply method for an engine that injects into an intake pipe of a feed engine, a shut-off valve controlled by an electronic control unit is arranged on the fuel inlet side of the vaporizer, and the vaporizer uses an electric heating unit as a heat source at the beginning of a low temperature start. An LPG fuel supply method characterized by limiting the inflow amount of LPG fuel.   2. The LPG fuel supply method for an engine according to claim 1, wherein the valve opening time is controlled via the electronic control unit based on predetermined data monitored using at least one or more types of sensors. .   The sensor includes at least a fuel pressure sensor disposed in the vaporizer or downstream thereof, and the shutoff valve is closed when the fuel pressure detected by the fuel pressure sensor exceeds a predetermined pressure. The LPG fuel supply method for an engine according to claim 2.   The valve opening time of the shut-off valve is obtained by calculating the data using a predetermined calculation formula in the electronic control unit. The amount of inflow of LPG fuel is determined by the vaporized gas generated as the temperature of the electric heater rises. The LPG fuel supply method for an engine according to claim 2 or 3, wherein LPG fuel is limited to a maximum storage amount that is not pushed out of the vaporizer. After warming up, the engine coolant is used as a heat source, and at the beginning of low temperature start, a vaporizer using an electric heating unit as a heat source, the shut-off valve disposed on the vaporizer inlet side of a fuel supply line, and the vaporizer or An LPG fuel supply device for an engine, comprising: a fuel pressure sensor disposed on the downstream side thereof; and an electronic control unit that controls opening and closing of the shutoff valve based on a signal from the fuel pressure sensor.

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